Playing in Group A, Tamil Nadu now have eight points in their coffers. The southern side had earlier defeated Assam in their opening match yesterday.
Sent into bat, Tamil Nadu piled up a huge 312 for the loss of seven wickets in 50 overs and then bowled out Mumbai for 286 in 44.2 overs.
Tamil Nadu rode on half-centuries from Baba Aparajith (77), Baba Indrajith (60 not out), Murali Vijay (55) and R Sathish (52) to get past the 300-run mark.
Chasing the mammoth score, opener Akhil Herwadkar (107) century went in vain as Mumbai failed to cross the final hurdle.
Herwadkar century came off 86 balls with the help of 16 boundaries and one six.
Besides Herwadkar, Shreyas Iyer (44) and Siddhesh Lad (47) were the two other batsmen to have scored significant runs for Mumbai.
Leg-spinner Murugan Ashwin (3/38) was the pick of bowlers for Chennai with three wickets while pace duo of Rahil Shah (2/55) and M Mohammed (2/68) shared four wickets between them.
Tamil Nadu: 312 for seven in 50 overs (Baba Aparajith 77, Baba Indrajith 60 not out, Murali Vijay 55, R Sathish 52; Dhawal Kulkarni 3/47).
Mumbai: 286 all out in 45.2 overs (Akhil Herwadkar 107; Murugan Ashwin 3/38).
